1. Field of the Invention
The present invention relates to a method for storing video data on digital video recorders, and more particularly, to a method for prioritizing such data and overwriting previously recorded data according to predefined rules provided by the operator.
2. Description of the Prior Art
Video data is made up of numerous individual digital pictures, sometimes referred to as frames. These frames are still pictures, and must be run sequentially at high speeds to create the effect of motion within the video. The file size of each frame varies, depending upon its quality, dimensions, and other characteristics. The combination of these frames into a single video data file or stream results in the video data having a high volume of information, and consequently, a large file size. This file size increases with the duration, quality, dimensions, and other characteristics of the video. As a result, video data is generally larger in size than its traditional data file counterparts, even after compression routines are performed upon it. Therefore, applications involving the creation or maintenance of video data often require larger and/or more efficient storage means.
Digital video recorders store video data upon various storage media for future selectable review. These media are generally designed to hold anywhere from several hours to several weeks of video images. However, all media have finite capacities. Once such capacities are reached, the operator must insert new (empty) media into the video recorder, or recycle the current media for subsequent reuse. Depending upon the sheer volume of video data received by the recorder, the former alternative may become cost-prohibitive within a short period of time.
Accordingly, reusing or recycling the media is commonly implemented. However, devices implementing such an alternative generally overwrite the existing video data in a sequential manner. This means that, once a storage medium is full, the recorder simply returns to the first sector of the medium and overwrites the existing video data from that point onward. Such a method does not take into consideration the potential importance or value of the data being overwritten—it simply overwrites the existing data in a sequential manner without regard to any priority the data may have. The result is that non-essential video may be retained, while essential video is deleted, simply because the essential events were recorded earlier in time.
It is therefore desirable to provide a method of reusing or recycling video data storage capacity once the storage medium has become full by overwriting the existing video data with new data such that the existing data is prioritized, so that existing low-priority data is overwritten instead of, or prior to, existing high-priority data. It is further desirable that the method be capable of receiving a real-time video data stream, and overwriting the existing data in real-time. It is further desirable that the priority of such existing data be redefinable in real-time.